The present invention relates to a paper feeding device of an image forming apparatus which is disposed at a stack bypass portion of the image forming apparatus for continuously feeding stacked paper pieces.
Conventionally, a paper feeding device of the type above-mentioned employs a so-called friction pad separating system in which a friction pad is pressed to and contacted with the top surface of stacked paper pieces, causing the highest paper piece to be separated from the remaining paper pieces.
However, the friction pad separating system requires a number of component elements such as spring clutch means, solenoid means and the like. This complicates the structure and increases the production cost.
Further, paper powder sticking to the friction pad, lowers frictional resistance applied to paper, thus causing the highest paper piece to be defectively separated from other stacked paper pieces. To prevent such a defective separation, it is required to carry out, relatively often, a maintenance such as replacement of the friction pad or the like.
In the friction pad separating system, it is required to replenish paper pushed between the friction pad and a roller or the like opposite thereto. This disadvantageously lowers the maneuverability of paper replenishment.
On the other hand, there is often used, as a clutch mechanism to be used in a paper feeding device or the like, a spring clutch system in which a solenoid is operated, as necessary, to reduce a coil spring in diameter, and the coil spring is wound on a boss at the drive or driven side, so that a drive force is to be transmitted.
However, when a metallic coil spring is used in this spring clutch system, the boss at the side with which the coil spring comes in slide contact (the drive input side) is required to be made of metal having a smooth surface. Accordingly, the surface is required to be polished, resulting in an increase in production cost.
On the other hand, when a resin spring is used, the boss is not required to be made of metal. However, the load to be applied cannot be so great. Accordingly, a drive force to be transmitted is small.
When such spring clutches are used in paper feeding devices, the positions where the paper feeding rollers are stopped, vary front one another with variations of dimensional precision of the boss diameters or the spring diameters, regardless of the bosses made of metal or resin. Accordingly, it is required, at the time of assembling, to properly adjust the paper feeding roller's stop positions by a method of adjusting the spring engagement positions or the like.